Redd, averaging 21.4 points a game, said he came down on teammate Luke Ridnour's foot after missing a shot near the basket with 4:16 left in the third quarter. He immediately winced, and limped about 30 feet before falling to the court for a few seconds. He then limped off the court and didn't return.
"I landed on his foot and it twisted, so I knew it was hurt," said Redd, who was on crutches after the game.
Redd, who finished with 14 points in 26 minutes, missed 14 games in November with a sprained right ankle.
"It's part of the game," he said. "When you play hard, things like this happen. I'm disappointed, but you know what, I'm going to be OK. I've had numerous injuries over the years and I'll be back."
The Bucks went 5-9 when Redd was out with the sprained ankle.
"That's not good news," teammate Charlie Villanueva said of Redd's injury. "We'll try to get him back healthy as soon as we can. Mike is a big part of the team and what we're doing."
Andrew Bogut, the team's starting center, has missed 13 games this year, including the last six with back spasms.
"Over half our games have been without two of our main players," coach Scott Skiles said. "Our guys are hanging in there. It's not always pretty every night, but we're hanging in there."
Information from the Associated Press was used in this report